Effects of cis-dichlorodiammineplatinum(II) on human colon carcinoma cells in vitro.

The lethal effects of cis-dichlorodiammineplatinum(II) were investigated on an established human colon carcinoma cell line. cis-Dichlorodiammineplatinum(II) was one of the most efficient antineoplastic agents tested thus far on this human colon carcinoma cell line. Survival of exponentially growing cells exposed to increasing concentrations of the drug (both in medium or in Hanks' balanced salt solution) was of the threshold exponential type (Dq = 1.2 microgram/ml, 1 hr; Do = 3.5 microgram/ml, 1 hr). Stationary-phase cells were extremely sensitive to the drug, and the survival curve demonstrated a simple exponential pattern (Do = 3.9 microgram/ml, 1 hr). Long-term exposure to low concentrations of cis-dichlorodiammineplatinum induced a high degree of killing, with only 0.5% of the cells surviving after incubation for 24 hr with 2 microgram/ml. Cells were unable to recover from potentially lethal or sublethal damages induced by the drug.